JP4982500B2 - Active matrix field emission display - Google Patents

Description

  The present invention relates to a field emission display (FED) in which a field emission device is applied to a flat panel display. More specifically, the present invention improves the uniformity of thin film transistors and pixels by using a plurality of thin film transistors connected in series. The present invention relates to an active matrix field emission display.

  In general, a field emission display includes a cathode plate having a field emitter array and an anode plate having a phosphor in parallel with each other at a narrow interval, for example, within 2 mm. It is an apparatus that is manufactured by packaging and displays an image by cathodoluminescence of the phosphor by causing electrons emitted from the field emitter of the cathode plate to collide with the phosphor of the anode plate. Such a field emission display has recently been researched and developed as a flat panel display that replaces a conventional cathode ray tube (CRT).

  The efficiency of field emitters, which are the core components of field emission displays, varies greatly depending on the device structure, emitter material, and emitter pattern. At present, the structure of a field emission device can be broadly divided into a bipolar structure composed of a cathode and an anode, and a tripolar structure composed of a cathode, a gate and an anode. In the tripolar electron-emitting device, the cathode or field emitter performs the function of emitting electrons, the gate performs the function of inducing electron emission, and the anode performs the function of receiving the emitted electrons. In the tripolar structure, electrons are emitted by an electric field applied between the cathode and the gate, and therefore, it can be driven at a lower voltage than the bipolar structure, and has an advantage that electron emission can be easily controlled. Due to these advantages, many field emission displays having a three-pole structure have been developed recently.

  Field emitter materials include metals, silicon, diamond, diamond-like carbon, carbon nanotubes, and carbon nanofibers. Recently, carbon nanotubes and nanofibers themselves are fine. Because it is sharp and has excellent safety, it is often used as an emitter material.

  FIG. 1 is a cross-sectional view illustrating a pixel configuration of a conventional passive-matrix field emission display, and a conventional carbon field emitter made of carbon nanotubes or carbon nanofibers and a passive matrix field emission display using the same. The pixel configuration of is shown.

  FIG. 2 is a schematic diagram showing the configuration of the cathode plate of the conventional passive matrix field emission display shown in FIG. 1, and is a schematic diagram showing the configuration of the field emitter array of the cathode plate.

  Referring to FIG. 1, a conventional passive matrix field emission display includes a glass substrate 11, a field emitter electrode 12 formed on a part of the glass substrate 11, and a part of the field emitter electrode 12. A carbon field emitter 13 formed, a gate insulating film 15 having a gate hole 14 surrounding the carbon field emitter 13, and a field emission gate electrode 16 formed on a part of the gate insulating film 15 are provided. Cathode plate 10a, another glass substrate 17, and red (R), green (G), and blue (B) phosphors 18 formed on a part of the glass substrate 17. The anode plate 10b is vacuum-packaged in parallel while facing each other.

  As shown in FIG. 2, the cathode plate 10a described above has a matrix form in which the field emitter electrode 12 and the field emission gate electrode 16 intersect each other, and a region formed by the intersection is one pixel. (Pixel) is defined, and each pixel is composed of a plurality of carbon field emitters 13.

  In the conventional passive matrix field emission display described above, since the gate hole 14 surrounding the carbon field emitter 13 is large and the gate insulating film 15 is thick, the driving voltage for field emission is much higher at 50 V or more. However, there is a problem that electrons are emitted non-uniformly not only between pixels but also inside the pixels. Further, since it is difficult to form the carbon field emitter 13 symmetrically with respect to the gate hole 14, there is a problem that the emitted electrons frequently flow into the field emission gate electrode 16 to form a leakage current. .

  For example, Patent Document 1 and Patent Document 2 have proposed techniques for solving the problems of such passive matrix field emission displays. The proposed technique will be briefly described below.

  FIG. 3 is a cross-sectional view showing a pixel configuration of a conventional active-matrix field emission display, and FIG. 4 is a schematic diagram showing a cathode plate configuration of the conventional active matrix field emission display shown in FIG. It is a road map.

  Referring to FIG. 3, a conventional active matrix field emission display is formed on a glass substrate 21, a thin film transistor 22 formed on a part of the glass substrate 21, and a part of a drain electrode of the thin film transistor 22. Carbon field emitter 23, gate insulating film 25 having gate hole 24 surrounding carbon field emitter 23, and field emission gate electrode 26 formed on part of gate insulating film 25. A cathode plate 20a, another glass substrate 27, and red (R), green (G), and blue (B) phosphors 28 formed on a part of the glass substrate 27; And an anode plate 20b which is vacuum-packaged in parallel while facing each other.

  As shown in FIG. 4, the cathode plate 20 a of the field emission display described above includes a thin film transistor connected in series with the carbon field emitter 23 to each of a plurality of pixels in a matrix form. The carbon field emitter 23 of each pixel is configured corresponding to one common field emission gate electrode 26. According to the configuration described above, the conventional active matrix field emission display induces electron emission from the field emitter 23 by applying a voltage to the field emission gate electrode 26 and simultaneously emits by applying a high voltage to the anode plate 20b. An image is displayed by accelerating the generated electrons with high energy. At this time, the scan of the display and the data signal are addressed to the thin film transistor.

  In the conventional active matrix field emission display described above, the field emission driving voltage can be lowered to the driving voltage of the thin film transistor as compared with the passive matrix field emission display, and the uniformity between pixels can be further improved.

  However, the conventional active matrix field emission display described above has a uniform uniformity inside the pixel because one thin film transistor controls the current of the field emitter for each pixel, and the source-drain leakage of the thin film transistor. The electric field emission current cannot be properly cut off by the current, which deteriorates the light / dark ratio of the display. In particular, if the voltage required for field emission is high, a high voltage is applied to the drain of the thin film transistor, so that the source-drain leakage current may become much larger.

Korean Published Patent No. 2004-0057866 Republic of Korea Published Patent No. 2005-0057712

  Accordingly, the present inventor proposes an active matrix field emission display capable of solving the problems of the conventional active matrix field emission display as described above.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide first and second thin film transistors connected in series in each pixel and a part of the drain electrode of the second thin film transistor. It is an object of the present invention to provide an active matrix field emission display capable of greatly improving the uniformity between thin film transistors and pixels.

  Another object of the present invention is to improve uniformity between thin film transistors and pixels by utilizing a high voltage thin film transistor with a thin film transistor coupled to a field emitter among a plurality of thin film transistors connected in series within each pixel. In addition, it is an object of the present invention to provide an active matrix field emission display capable of greatly reducing the source-drain leakage current of a thin film transistor.

  Still another object of the present invention is to greatly improve the uniformity inside a pixel by individually or group-controlling a plurality of field emitters in the pixel using a plurality of thin film transistors connected in series. It is an object of the present invention to provide an active matrix field emission display capable of greatly improving the light / dark ratio of the display.

  According to a preferred aspect of the present invention for achieving the above object, the substrate, the first and second thin film transistors connected in series on the substrate, and the drain electrode of the second thin film transistor are positioned. A cathode plate comprising a field emitter, a gate insulating film having a gate hole surrounding the field emitter, a field emission gate electrode positioned on the gate insulating film, a substrate, and a red color positioned on the substrate There is provided a field emission display comprising (R), green (G) and blue (B) phosphors, and an anode plate which is vacuum-packaged in parallel while facing the cathode plate. The

  Preferably, source and drain electrodes of the first thin film transistor and the second thin film transistor are connected in series with each other, and the gate electrodes of the first thin film transistor and the second thin film transistor may be common or separate. .

  The second thin film transistor is a high voltage transistor that can withstand a drain voltage of 25 V or more.

  Each pixel of the cathode plate includes a first thin film transistor and a plurality of second thin film transistors. If each pixel comprises a plurality of second thin film transistors, each second thin film transistor can have a separate field emitter, and the field emitter can have a common or separate field emission gate electrode.

  The active layer of the first thin film transistor and the second thin film transistor is made of amorphous silicon (a-Si), microcrystalline silicon (mc-Si), polycrystalline silicon (poly-Si), or ZnO. It has such a wide band gap or is made of an organic semiconductor.

  The field emitter is formed of a film type (thin film or thick film) made of diamond, diamond-like carbon, carbon nanotube, carbon nanofiber, etc., and is formed by a chemical vapor deposition (CVD) method or the like. It can be formed by direct growth or a paste method using powder.

  The physical size of the gate hole and gate insulating film surrounding the field emitter is much larger and thicker than the field emitter.

  The gate insulating film having the gate hole and the field emission gate electrode may be manufactured on a substrate different from the cathode plate and may be combined during vacuum packaging.

  According to the present invention, a pixel of a field emission display is constituted by first and second thin film transistors connected in series, and a field emitter formed on a part of the drain electrode of the second thin film transistor. In addition, the uniformity inside the pixel can be greatly improved, and the first and second thin film transistors connected in series can increase the resistance to high voltage and greatly improve the lifetime of the field emission display. Furthermore, the structure of the first and second thin film transistors connected in series can greatly reduce the source-drain leakage current inherent in the thin film transistor, thereby greatly improving the light / dark ratio of the field emission display.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention.

  FIG. 5 is a cross-sectional view illustrating an embodiment of a pixel configuration of an active matrix field emission display according to the present invention.

  As shown in FIG. 5, the field emission display according to the present invention includes a glass substrate 110 and a first thin film transistor 120 (T1) and a second thin film transistor connected in series on a part of the glass substrate 110. 130 (T2), the field emitter 140 formed on part of the drain electrode of the second thin film transistor 130, the gate home 150 and the gate insulating film 160 surrounding the field emitter 140, and the gate insulating film 160 A cathode plate 100a having a field emission gate electrode 170 formed on a part of the glass substrate 180, another glass substrate 180, and red, green, and blue formed on a part of the glass substrate 180. And an anodic plate 100b provided with a phosphor 190 of FIG. The cathode plate 100a and the anode plate 100b are vacuum packaged in parallel while facing each other.

  The first thin film transistor 120 includes a thin film transistor gate 121 formed of a metal or an alloy on a part of the glass substrate 110, and an amorphous silicon nitride film (a-SiNx) or silicon on the glass substrate 110 including the gate 121. The gate insulating film 122 of the thin film transistor formed of an oxide film, the active layer 123 of the thin film transistor formed of amorphous silicon (a-Si) on the gate 121 and part of the gate insulating film 122, and the active layer 123 The source 124 and drain 125 of the thin film transistor formed of n-type amorphous silicon at both tip regions thereof, and the source electrode 126 of the thin film transistor formed of metal or alloy on the source 124 and part of the gate insulating film 122 And a thin film formed of metal or alloy on the drain 125 and part of the gate insulating film 122 It is composed of a drain electrode 127 of the transistor.

  The second thin film transistor 130 includes a thin film transistor gate 131 formed of a metal or an alloy on a part of the glass substrate 110, and an amorphous silicon nitride film (a-SiNx) or a glass substrate 110 including the gate 131. A gate insulating film 132 of the thin film transistor formed of a silicon oxide film, an active layer 133 of the thin film transistor formed of amorphous silicon (a-Si) on a part of the gate 131 and the gate insulating film 132, and an active layer A thin film transistor source 134 and drain 135 formed of n-type amorphous silicon at both tip regions of 133, and a thin film transistor source electrode formed of metal or an alloy on part of the source 134 and gate insulating film 132 136, a thin film formed of a metal or an alloy on part of the drain 135 and the gate insulating film 132. It is composed of a drain electrode 137 of the transistor.

  The gate insulating film 122 of the first thin film transistor 120 and the gate insulating film 132 of the second thin film transistor 130 are continuously connected to each other with the same material, and the drain electrode 127 of the first thin film transistor 120 is connected to the first thin film transistor 120. The gate electrodes 121 and 131 of the first and second thin film transistors 120 and 130 are connected to each other or formed separately from each other.

The second thin film transistor 130 is a high voltage thin film transistor that can withstand a drain voltage of 25 V or more by having an offset length (L _off ) in which the gate 131 and the drain 135 do not overlap each other vertically. It is formed.

  The field emitter 140 is formed of a film type made of diamond, diamond-like carbon, carbon nanotube, carbon nanofiber, etc., for example, a thin film or a thick film, and is directly grown by chemical vapor deposition or powder. It can be formed by the paste method used.

  The physical size of the gate home 150 and the gate insulating film 160 is larger and thicker than the field emitter 140, and can be configured to be 1 to 100 times, for example. In addition, the gate insulating film 160 having the gate hole 150 and the field emission gate electrode 170 can be manufactured on a substrate different from the cathode plate 110a and can be combined at the time of vacuum packaging.

  FIG. 6 is a schematic diagram showing the configuration of the cathode plate of the active matrix field emission display shown in FIG.

  As shown in FIG. 6, the gate electrodes of the first and second thin film transistors are connected to row bus lines (R1, R2, R3,...), And the source electrodes of the first thin film transistors are It is connected to a column bus (column bus; C1, C2, C3,...) Line, and the field emission gate electrode 170 of the field emitter is connected in common (G) to each pixel.

  The field emission display of this embodiment is driven by the following method. Scanning and data signals for driving the display are addressed to the gate and source electrodes of the first thin film transistor 120, respectively, and voltage is applied to the field emission gate electrode 170 to induce electron emission from the field emitter 140 and the anode plate. A high voltage is applied to the electron to accelerate the emitted electrons with the energy to express an image. At this time, the gray representation of the display is obtained by changing the pulse amplitude or the pulse width of the data signal. For reference, the scanning and data signals of the display can be addressed by changing the source and gate electrodes of the first thin film transistor 120, respectively.

  FIG. 7 is a schematic diagram illustrating a configuration of a cathode plate of an active matrix field emission display according to another embodiment of the present invention.

  FIG. 7 is basically the same as the embodiment of FIG. 6, but each pixel includes one first thin film transistor 120 and a plurality of second thin film transistors 130a, and the plurality of second thin film transistors 130a. The plurality of source electrodes are respectively connected in series to the drain electrode of the first thin film transistor 120. In addition, another field emitter 140a, 140b, 140c is connected to each drain electrode 137 of the second thin film transistor 130a, and each field emitter 140a, 140b, 140c corresponds to the common field emission gate electrode 170. The location is different.

  According to the above-described configuration, the uniformity inside the pixel can be greatly improved by using the plurality of second thin film transistors 130a connected in series to the first thin film transistor 120, respectively.

  FIG. 8 is a schematic diagram illustrating a configuration of a cathode plate of an active matrix field emission display according to still another embodiment of the present invention.

  FIG. 8 is basically the same as the embodiment of FIG. 7, but a plurality of electric fields corresponding to the plurality of field emitters 140a, 140b, 140c respectively connected to the drain electrodes of the plurality of second thin film transistors 130a. The difference is that the emission gate electrodes 170a, 170b, and 170c are independently positioned.

  According to the configuration described above, the uniformity between pixels can be greatly improved by controlling a plurality of field emitters individually or in groups within each pixel.

  The present invention described above can be variously replaced, modified, and changed without departing from the technical idea of the present invention as long as it has ordinary knowledge in the technical field to which the present invention belongs. Therefore, the present invention is not limited to the above-described embodiment and attached drawings.

FIG. 2 is a cross-sectional view illustrating a pixel configuration of a conventional passive-matrix field emission display. FIG. 2 is a schematic diagram showing a configuration of a cathode plate of the conventional passive matrix field emission display shown in FIG. 1. FIG. 6 is a cross-sectional view illustrating a pixel configuration of a conventional active-matrix field emission display. FIG. 4 is a schematic diagram showing a configuration of a cathode plate of the conventional active matrix field emission display shown in FIG. 3. FIG. 3 is a cross-sectional view illustrating an example of a pixel configuration of an active matrix field emission display according to the present invention. FIG. 6 is a schematic diagram illustrating a configuration of a cathode plate of the active matrix field emission display illustrated in FIG. 5. FIG. 6 is a schematic diagram illustrating a configuration of a cathode plate of an active matrix field emission display according to another embodiment of the present invention. FIG. 6 is a schematic diagram illustrating a configuration of a cathode plate of an active matrix field emission display according to still another embodiment of the present invention.

Claims (12)

Gate insulation having a substrate, first and second thin film transistors connected in series on the substrate, a field emitter located on the drain electrode of the second thin film transistor, and a gate hole surrounding the field emitter A cathode plate comprising a film and a field emission gate electrode formed on the gate insulating film;
A field emission display comprising: a substrate; and an anode plate that is provided with red, green, and blue phosphors positioned on the substrate and vacuum-packaged in parallel while facing the cathode plate. And
Each pixel of the cathode plate includes a first thin film transistor and a plurality of second thin film transistors, and the plurality of second thin film transistors are connected to different field emitters, respectively. display.   The source and drain electrodes of the first thin film transistor and the second thin film transistor are connected in series with each other, and the gate electrodes of the first thin film transistor and the second thin film transistor are commonly or individually positioned. The field emission display according to claim 1, wherein the field emission display is provided.   The field emission display according to claim 1, wherein the second thin film transistor includes a high voltage transistor capable of withstanding a drain voltage of 25V or more.   4. The field emission display according to claim 3, wherein the second thin film transistor has an offset length in which a gate and a drain do not overlap each other vertically.   The active layer of the first thin film transistor and the second thin film transistor is at least selected from a group including a semiconductor having a wide band gap such as amorphous silicon, microcrystalline silicon, polycrystalline silicon, and ZnO, and an organic semiconductor. 2. The field emission display according to claim 1, wherein the field emission display is made of one material. 2. The field emission display according to claim 1 , wherein each field emitter connected to the second thin film transistor is located corresponding to a common or separate field emission gate electrode.   The field emission display of claim 1, wherein the field emitter is made of at least one carbon material selected from the group including diamond, diamond-like carbon, carbon nanotube, and carbon nanofiber. The field emission display of claim 7 , wherein the carbon field emitter is formed by direct growth using chemical vapor deposition or a paste method using powder.   The field emission display according to claim 1, wherein the thickness of the gate insulating film is not less than 1 and not more than 100 times the thickness of the field emitter.   The gate insulating film having the gate hole and the field emission gate electrode are manufactured on a substrate different from the cathode plate and vacuum-packaged together with the cathode plate and the anode plate. The field emission display according to claim 1.   Scanning and data signals for driving the display are addressed to the gate and source electrodes of the first thin film transistor, respectively, and voltage is applied to the field emission gate electrode to induce electron emission from the field emitter and the anode. 2. The field emission display according to claim 1, wherein an image is displayed by accelerating electrons emitted by applying a high voltage to the plate with its energy. 12. The field emission display according to claim 11 , wherein the gradation expression of the display is obtained by changing a pulse amplitude or a pulse width of the data signal.

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